The present invention relates to a system for degassing fluids and, more particularly, to a system for removing gas from drilling mud without allowing said gas to escape to the atmosphere before the gas is treated to prevent contamination.
Under many circumstances, it is desirable and in fact often absolutely essential that gases be removed from drilling mud without allowing the gas to escape into the atmosphere. During the drilling of an oil well, the drilling mud that is circulated through the borehole frequently becomes contaminated with gases encountered in the formations. Since it is economically unfeasible to discard the contaminated drilling mud and because of the danger of the gases in the drilling mud escaping into the atmosphere creating dangerous conditions at the drill site, it is necessary to process the drilling mud to remove the gases and recirculate the degassed drilling mud through the borehole. The contaminating gases may be poisonous or highly explosive. The release of such gases into the atmosphere would present a substantial risk to personnel to the drilling area. The presence of gases in the drilling mud decreases its weight and viscosity and renders it unsuitable for recirculation through the borehole. When gases are contained in the drilling mud being circulated through the borehole, it increases the danger of a blowout in the well.
A "Notice to Lessees and Operators of Federal Oil and Gas Leases in the Outer Continental Shelf, Gulf of Mexico Area" was released May 7, 1974 by the United Stated Department of the Interior Geological Survey Gulf of Mexico area, relating to hydrogen sulfide in drilling operations. The notice outlines requirements for drilling operations when there is a possibility or probability of penetrating reservoirs known or expected to contain hydrogen sulfide. Section 3, f. provides that "drilling mud containing H.sub.2 S gas shall be degassed at the optimum location for the particular rig configuration employed. The gases so removed shall be piped into a closed flare system and burned at a suitable remote stack."
It is desirable that any system for removing gas from drilling mud without allowing said gas to escape to the atmosphere contain alarms that will be actuated should conditions exceed a pre-determined level. The actuation of the alarms will allow proper procedures to be taken to correct the problem. The system must be totally enclosed and of a fail-safe design. The system must start at the wellhead and contain the gas within the system until it is treated at a flare or disposed of by other means. In order for the degassing system to operate effectively, it is essential that a partial vacuum be maintained in the degassing vessel at all times. In addition, controlled flow rates should be provided to the degassing vessel to insure efficient operation of the degassing system.